This invention relates to the fabrication of wire from particulate matter. This invention relates more particularly to the fabrication of wire from particulate matter using laser deposition technology.
Wire has been made by melting the metal or alloy from which the wire is to be formed, casting an ingot from the molten metal or alloy, processing the ingot in a rolling mill, and drawing the rolled metal or alloy through a forming die into the desired wire diameter. Extrusion process for making wire are also available. These methods generally require use of heavy equipment and tools, heat treatments for casting, forging, drawing, or extruding or both, and annealing. The traditional methods also generally require many iterative sequences of steps to achieve the final diameters of wire.
The types of material from which the wire can be made by traditional multi-step processes are also limited to metals or alloys which can be plastically deformed and extruded and economically processed by these methods. Brittle, low ductility materials do not easily lend themselves to deformation processing. Expensive wire drawing dies are subject to abrasion in using traditional manufacturing methods to make wire of hard or abrasive materials.
Conventional processing of metals or alloys into wires can result in contamination which can significantly affect the mechanical or metallurgical properties of the finished wires.
There have been developed methods of making articles using metal powder melted by a laser beam, as disclosed in U.S. Pat. No. 4,724,299. U.S. Pat. No. 5,111,021 discloses addition of material to a surface using a laser beam and metal powder. Although these patents disclose cladding or encrusting existing surfaces on articles, they do not disclose formation of defined wire.
U.S. Pat. No. 4,743,733 discloses repair of an article by directing a laser beam and a stream of metal powder to a region of the article which needs repair. These repair methods rely on support of the molten pool by a previously existing substrate of the article being repaired.
U.S. Pat. No. 4,323,756 discloses a method for producing complex metallic articles from metal powders and substrates which become part of the articles. A focused energy beam is used to create a molten pool on a substrate and metal powder is supplied to a point outside of the area at which the beam impinges upon the substrate. Movement of the substrate then carries the powder into the beam and molten pool, where it melts and mixes with the melted substrate material.
There is a need for methods of making wire in fewer processing steps and which can use simpler equipment which operates to provide movement along a single axis. There is also a need for methods of making wire which do not require extreme operating conditions, heavy equipment and large capital outlays. Methods and apparatuses are needed for making wire from more different types of materials than can easily be processes in the traditional manufacturing methods and apparatuses. There is also a need for ways of reducing or eliminating contaminants in wire products.
Therefore, it is an object of this invention to provide a single-step method of making wire.
It is another object of this invention to provide a method of making wire from a larger variety of materials than the metals and alloys from which wire is now made.
It is yet another object of this invention to provide a method of making wire which reduces or eliminates contamination of the wire articles.
It is a further object of this invention to provide a laser deposition process for making wire.
It is a still further object of this invention to provide a method of making wire with specific properties such as microstructural or magnetic orientation.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, there has been invented a method of making wire from materials in particulate form comprising:
(a) defining the shape and dimensions of the wire;
(b) creating control commands effective to form the wire by deposition of molten material along a deposition path in a single axis;
(c) focusing a laser beam at a location within a deposition zone;
(d) providing particulate material to the deposition zone;
(e) forming a pool of molten material in the deposition zone by melting a portion of an article support and the particulate material by means of energy provided by the laser beam;
(f) depositing molten material from the deposition zone on the article support at points along a first portion of the deposition path by moving the deposition zone along the deposition path in order to form a solid portion of the wire which is adjacent to the article support;
(g) forming a pool of molten material in the deposition zone by melting a portion of the partially formed portion of wire and the particulate material by means of energy provided by the laser beam;
(h) depositing molten material from the deposition zone at points along a second portion of the deposition path by moving the deposition zone along the deposition path where the molten material solidifies after leaving the deposition zone, in order to continue formation of the wire; and
(i) controlling flow of particulate material into the deposition zone, energy density of the laser beam, and focal position of laser beam by means of the control commands as deposition takes place.
Alternatively, instead of withdrawing the laser deposition zone along the deposition path on the axis of the laser beam, as in steps (f) and (h), the deposition zone can be focused and held in constant position with the wire being withdrawn from the deposition zone as the wire is formed.
Provisions can be made for recycling any unused particulate material in the process.
In another embodiment, an apparatus for carrying out the process of this invention is provided. The inventive apparatus comprises:
(a) a means for defining the shape and dimensions of a wire, this means being capable of creating control commands effective to form a wire by depositions of molten material;
(b) a feed mechanism for introducing particulate material into a deposition zone;
(c) a laser positioned to focus a laser beam into the particulate material in the deposition zone;
(d) supporting and drawing device for moving the wire away from the deposition zone; and
(e) a controller for controlling flow of the particulate material, energy density of the laser beam, focal position of laser beam, and speed of withdrawal of the wire being formed from the deposition zone by using the control commands.
Alternatively, instead of having a supporting and drawing device to move the wire from the deposition zone, there is provided a device for moving the deposition zone along the axis of the laser beam away from the wire being formed.
Provisions can be made for recycling any unused particulate material in the apparatus.